Does intermittent fasting cause blood sugar swings?

Health Q & A with Dr. Michael Jacobson, D.O. 

Editor’s note: This information was published in the October 2019 issue of Heartfelt Magazine, CHM’s monthly magazine that provides CHM membership-related tips and tricks, medical advice from doctors, testimonies from CHM members, and more. Please refer to the CHM Guidelines and applicable web pages for the most up-to-date information regarding CHM membership, sharing eligibility, and ministry news.

Q: Each day I have been waiting until noon or 1 p.m. to eat, then limiting my calories to 950-1,100 per day. I also try to stay away from carbs. I’ve had a lot of unwanted fat disappear and I feel excellent. A friend of mine follows a similar diet where he only eats between 4 and 7 p.m. and has an unrestricted diet. He has had significant weight loss and excellent maintenance of that loss.

I heard that eating in narrow time windows can cause health problems from blood sugar spikes. Some articles have suggested that this is counterproductive. Other articles state that it’s beneficial to allow the stomach and digestion an opportunity to rest.

What are your thoughts about eating only in a three or six-hour time window?

A: Great question! The short answer to your question is: it depends. If an individual has a medical condition such as diabetes—in which tight blood sugar control is required (especially if it’s being monitored throughout the day and requires insulin based on blood sugar values and dietary intake)—then yes, an intermittent fasting diet lifestyle may not be the best option.

However, in most cases, diabetes mellitus is not caused by an inadequate production of insulin (by the pancreas), but by insulin resistance, which is typically tied to excess abdominal fat. In many of these “Type 2” cases, insulin administration is not part of the treatment regimen. If the diet results in significant loss of unwanted belly fat, then the insulin resistance problem may very well disappear along with the undesired weight and blood sugar problems.

In general, if someone experiences progressive weight loss toward their ideal weight goal and is feeling well, they are probably on the right track. I suggest that you stay in close communication with your family physician through this process. Most doctors will be very supportive of what you’re accomplishing!

Please note: My office requires a one week turnaround for medical information. If you have an acute or emergency medical incident, please seek immediate medical attention.

If you have a health question for Dr. Jacobson, CHM Medical Director, please email it to This information is not intended to replace the advice of your physician.

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